Mechanical Response of Two Carbonate Sediments From Australia’s North West Shelf

2014 ◽  
Author(s):  
Barry M. Lehane ◽  
J. Antonio H. Carraro ◽  
Nathalie Boukpeti ◽  
Sarah Elkhatib
Keyword(s):  
Water Content ◽  
Simple Shear ◽  
Void Ratio ◽  
Mechanical Response ◽  
Carbonate Sediments ◽  
Fines Content ◽  
North West ◽  
The North ◽  
Undrained Strength

The carbonate sediments found offshore on the North West Shelf of Australia can generally be described as silts with varying proportions of clay-sized and sand-sized carbonate particles. This paper investigates the undrained shearing response (as measured under simple shear and triaxial conditions) of two sediments with different grading curves. The importance of the fines content in controlling the density and hence dilatancy and undrained strength of the materials is demonstrated. The paper discusses the importance of fabric to the behavior of these soils and provides guidance on how undrained strengths of soils of this nature may be assessed with a knowledge of a material’s in-situ water content (or void ratio) and composition.

Combining ExoMars’ Ma_MISS and Drill data

2020 ◽  
Author(s):  
Alessandro Frigeri ◽  
Maria Cristina De Sanctis ◽  
Francesca Altieri ◽  
Simone De Angelis ◽  
Marco Ferrari ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Water Content ◽  
Large Scale ◽  
Mechanical Response ◽  
European Space Agency ◽  
Volcanic Rocks ◽  
Space Agency ◽  
Geophysical Imaging

<p>The ExoMars Rover and Surface Platform planned for launch in 2022 is a large international cooperation between the European Space Agency and Roscosmos with a scientific contribution from NASA.  Thales Alenia Space is the ExoMars mission industrial prime contractor. </p> <p>Besides sensors and instruments characterizing the surface at large scale, the ExoMars’ rover Rosalind Franklin payload features some experiments devoted specifically to the characterization of the first few meters of the Martian subsurface. These experiments are particularly critical for the main ExoMars objective of detecting traces of present or past life forms on Mars, which may have been preserved within the shallow Martian underground [1].</p> <p>Rosalind Franklin will be able to perform both non-invasive geophysical imaging of the underground [2] and subsurface <em>in situ</em> measurements thanks to the Drill unit installed on the rover. The Drill has been developed by Leonardo and its purposes are 1) to collect core samples to be analyzed in the Analytical Laboratory Drawer (ALD) onboard the Rover and 2) to drive the miniaturized spectrometer Ma_MISS within the borehole.   </p> <p>Ma_MISS (Mars Multispectral Imager for Subsurface Studies, [3]) will collect mineralogic measurements from the rocks exposed into the borehole created by the Drill with a spatial resolution of 120 μm down to 2 meters into the Martian subsurface.</p> <p>Rocks are composed of grains of minerals, and their reaction to an applied stress is related to the mechanical behavior of the minerals that compose the rock itself. The mechanical properties of a mineral depend mainly on the strength of the chemical bonds, the orientation of crystals, and the number of impurities in the crystal lattice.</p> <p>In this context, the integration of Ma_MISS measurements and drill telemetry are of great importance.  The mechanical properties of rocks coupled with their mineralogic composition provide a rich source of information to characterize the nature of rocks being explored by ExoMars rover’s drilling activity.</p> <p>Within our study, we are starting to collect telemetry recorded during the Drill unit tests on several samples ranging from sedimentary to volcanic rocks with varying degrees of weathering and water content.  In this first phase of the study, we focused our attention on the variation of torque and penetration speed between different samples, which have been found to be indicative of a particular type of rock or group of rocks and their water content.  </p> <p>We are planning to analyze the same rocks with the Ma_MISS breadboard creating the link between the mineralogy and the mechanical response of the Drill.      </p> <p>This will put the base for a more comprehensive and rich characterization of the <em>in situ</em> subsurface observation by Rosalind Franklin planned at Oxia Planum, Mars in 2023. </p> <p> </p> <p><strong>Acknowledgments: </strong>We thank the European Space Agency (ESA) for developing the ExoMars Project, ROSCOSMOS and Thales Alenia Space for rover development, and Italian Space Agency (ASI) for funding the Ma_MISS experiment (ASI-INAF contract n.2017-48-H.0 for ExoMars MA_MISS phase E/science).</p> <p> </p> <p><strong>References</strong></p> <p>[1] Vago et al., 2017. Astrobiology, 17 6-7. [2] Ciarletti et al., 2017. Astrobiology, 17 6-7. [3] De Sanctis et al., 2017. Astrobiology, 17 6-7.</p>

Estimating the undrained strength of sand: a theoretical framework

1995 ◽  
Vol 32 (5) ◽  
pp. 859-870 ◽  
Author(s):  
Catherine E. Fear ◽  
Peter K. Robertson
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Void Ratio ◽  
Triaxial Compression ◽  
State Parameter ◽  
In Situ Tests ◽  
Initial State ◽  
Undrained Strength

A framework for estimating the ultimate undrained steady state shear strength of sand (Su) from in situ tests, which combines the theory of critical state soil mechanics with shear wave velocity measurements, is presented. For a particular direction of undrained loading, samples of a given sand at a constant void ratio will reach the same Su, despite the magnitude of the initial effective confining stresses. Unique Su/p′ or [Formula: see text] ratios for a given direction of loading exist for a particular sand only if state parameter is constant throughout the deposit. Normalized shear wave velocity, Vs1, can be correlated with void ratio and is therefore used to estimate Su for a given initial state and direction of loading. Strengths in triaxial compression are examined in this paper; however, the same framework can be used to estimate strengths under other directions of loading. The Su–Vs1 relationship is shown to be relatively sensitive and should be used more as a screening tool rather than an accurate means of predicting Su. Vs1 is converted to equivalent values of SPT (N1)60 and CPT qc1, and the results are compared with the current methods of estimating Su. Key words : in situ testing, liquefaction, sand, undrained strength.

scholarly journals On the Late Pliocene stone tools of the Quranwala Zone, north-west sub-Himalayas, India

Antiquity ◽  
2017 ◽  
Vol 91 (357) ◽  
Author(s):  
Vidwan Singh Soni ◽  
Anujot Singh Soni
Keyword(s):  
Stone Tools ◽  
Fossil Bone ◽  
Question Mark ◽  
North West ◽  
Cut Marks ◽  
The North ◽  
Geological Processes ◽  
Animal Bones ◽  
Fossil Bones

A recent study of the Quranwala Zone (QZ) of the north-west sub-Himalayas, India, presents evidence for anthropic activity during the Pliocene that includes a number of stone tools found in association with fossil animal bones with cut marks. Based on the date of the Pliocene rock outcrop, the tools and bones are suggested to date from 2.6 Ma (Gaillard et al. 2016). There is, however, a question mark over the context of these tools within an outcrop of Pliocene rocks and, hence, over the date of these tools and the fossil bones. The trench from which they were excavated at Masol 2 (Gaillard et al.2016: fig. 3) lies in a depression at the bottom of a slope; the description provided in section 2 of the paper by Gaillard et al. (2016) suggests that the stone tools may not have been in situ within the Pliocene levels, but had accumulated there and were mixed with the fragments of fossil bone due to geological processes. Moreover, many of the stone tools, such as the ‘simple choppers’ found in association with the fossil animal bones (Gaillard et al.2016: figs 6, 8, 9), are usually found on much more recent sites and are therefore unlikely to date from 2.6 Ma.

Utility of a simple soil water budget model in agronomic research. 2. Estimates of available soil water in relation to profile changes of soil water content and potential

1974 ◽  
Vol 14 (66) ◽  
pp. 80 ◽  
Author(s):  
RG Fawcett ◽  
OG Carter
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Budget ◽  
Plant Density ◽  
Budget Model ◽  
North West ◽  
The North ◽  
South Wales ◽  
Profile Changes

A study was made of the effects of plant density, time-of-sowing and level of fallow water on profile changes in soil water content and potential during the growing season of spring wheat. The pattern of soil moisture extraction was affected by all treatments although water depletion occurred chiefly in the 0-90 cm zone. The results are discussed in relation to limitations of a simple soil water budget model and to wheat cropping on the north-west slopes and plains of New South Wales.

CALCULATION OF THE NATURAL FLOW REGULATION COEFFICIENT OF THE PREGEL RIVER

2020 ◽  
pp. 55-61
Author(s):  
V.A. Naumov ◽  
Keyword(s):  
Water Content ◽  
Approximate Method ◽  
Flow Distribution ◽  
Hydrological Regime ◽  
Flow Regulation ◽  
North West ◽  
The Past ◽  
The North ◽  
Natural Flow ◽  
Flood Flows

The average daily expenditure security curves are used to analyze the intra-annual flow distribution of rivers. The share of basic runoff is estimated using the natural flow regulation coefficient (NFRC). The value of NFRC is determined by the graph of the specified curve or another approximate method. The simple Mathcad-method for calculating NFRC is presented in the article. NFRC of The Pregel River over the past 12 years have been calculated. The presence of floods (summer-autumn rain and winter thaw) is a feature of the hydrological regime of the Southern Baltic rivers. The increase in the water content of the Pregel River is mainly due to floods. Flood flows greater than the runoff of spring floods in some years. Therefore, the increase in the water content of the Pregel River does not lead to a decrease in NFRC, as in other rivers in the North-West of Russia.

Strain Accumulation Procedure During Staged Cyclic Loading of Carbonate Sediments

2014 ◽  
Author(s):  
Nathalie Boukpeti ◽  
Barry Lehane ◽  
J. Antonio H. Carraro
Keyword(s):  
Shear Stress ◽  
Cyclic Loading ◽  
Shear Strain ◽  
Simple Shear ◽  
Soil Strength ◽  
Carbonate Sediments ◽  
Strain Accumulation ◽  
Shear Tests ◽  
Cyclic Shear ◽  
North West

Design of offshore foundation systems requires assessment of the effects of cyclic loading on the soil strength. This paper investigates the applicability of the strain accumulation procedure, which is used to assess the effects of wave loading on the soil strength. Staged undrained cyclic simple shear tests were conducted on a carbonate sediment from the North West shelf of Australia, with varying shear stress amplitude in each stage. The shear strain mobilised at the end of the staged tests is compared with the value predicted by the strain accumulation procedure, using shear strain contours constructed from the results of single amplitude undrained cyclic simple shear tests. It was found that the strain accumulation procedure gives adequate prediction for normalised cyclic shear stress less or equal to 0.3, but largely underestimates the cyclic shear strain for normalised cyclic shear stress greater than 0.3 (the cyclic shear stress being normalised by the effective vertical stress at the end of consolidation).

scholarly journals Model-based aviation advice on distal volcanic ash clouds by assimilating aircraft in-situ measurements

2016 ◽  
Author(s):  
G. Fu ◽  
A. W. Heemink ◽  
S. Lu ◽  
A. J. Segers ◽  
K. Weber ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Transport Model ◽  
Real Life ◽  
Forecast Accuracy ◽  
In Situ Measurements ◽  
North West ◽  
The North ◽  
Ash Plume ◽  
Potential Improvement

Abstract. The forecast accuracy of distal volcanic ash clouds is important for providing valid aviation advice during volcanic ash eruption. However, because the distal part of volcanic ash plume is far from the volcano, the influence of eruption information on this part becomes rather indirect and uncertain, resulting in inaccurate volcanic ash forecasts in these distal areas. In our approach, we use real-life aircraft in-situ observations, measured in the North-West part of Germany during the 2010 Eyjafjallajokull eruption, in an ensemble-based data assimilation system combined with a volcanic ash transport model to investigate the potential improvement on the forecast accuracy with regard to the distal volcanic ash plume. We show that the error of the analyzed volcanic ash state can be significantly reduced through assimilating real-life in-situ measurements. After a continuous assimilation, it is shown that the aviation advice for Germany, the Netherlands and Belgium can be significantly improved. We suggest that with suitable aircrafts measuring once per day across the distal volcanic ash plume, the description and prediction of volcanic ash clouds in these areas can be greatly improved.

WELL-BORE INSTABILITY IN THE NORTH WEST SHELF OF AUSTRALIA

1994 ◽  
Vol 34 (1) ◽  
pp. 1
Author(s):  
C.P. Tan ◽  
D.R. Willoughby ◽  
R.R. Hillis ◽  
S. Zhou ◽  
H-B Mühlhaus ◽  
...  
Keyword(s):  
Research Centre ◽  
Well Bore ◽  
Cooperative Research ◽  
Stress Regime ◽  
North West ◽  
The North ◽  
In Situ Stresses ◽  
Stress Changes ◽  
Contour Plots

Well-bore instability, experienced mainly in shales, has resulted in significant drilling delays and abandonment of wells in the North West Shelf of Australia. Although these problems may be induced by physico-chemical interactions, there is an increasing awareness that instability in this region is principally associated with in situ stresses that are high relative to the strength of the materials.This paper describes the research undertaken by the Australian Petroleum Cooperative Research Centre to assist industry in understanding and managing stress-induced well-bore instability in this region. To conduct such stability analyses the basic information required includes knowledge of the orientation and magnitude of the principal in situ stresses and the strength and deformation response of the materials to stress changes imposed by drilling. The required data can be determined using welllogging, analytical and laboratory techniques.Analytical methods can be used to examine the relationship between well-bore stability and changes introduced through drilling. Spreadsheets based on the analytical methods have been produced and applied to the assessment of drilling alternatives and/or design of some well-bores in the North West Shelf.The application of the critical mud weight contour plots and mud weight stability profiles produced by the spreadsheets in assessing drilling alternatives, selection of optimum well-bore alignment and mud weight design are demonstrated through examples. The analyses showed that counter to intuitive expectations, an inclined well may be more stable than a vertical well depending on the well-bore direction, deviation angle and stress regime.

scholarly journals Serendipitous In Situ Conservation of Faba Bean Landraces in Tunisia: A Case Study

Genes ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 236 ◽  
Author(s):  
Elyes Babay ◽  
Khalil Khamassi ◽  
Wilma Sabetta ◽  
Monica Marilena Miazzi ◽  
Cinzia Montemurro ◽  
...  
Keyword(s):  
Faba Bean ◽  
Agricultural Research ◽  
In Situ Conservation ◽  
Grain Legumes ◽  
Gene Bank ◽  
Genetic Constitution ◽  
Special Focus ◽  
North West ◽  
The North

Cultivation of faba bean (Vicia faba L.) in Tunisia is largely based on improved varieties of the crop. However, a few farmers continue to produce local cultivars or landraces. The National Gene Bank of Tunisia (NGBT) recently launched a collection project for faba bean landraces, with special focus on the regions of the North West, traditionally devoted to cultivating grain legumes, and where around 80% of the total national faba bean cultivation area is located. The seed phenotypic features of the collected samples were studied, and the genetic diversity and population structure analyzed using simple sequence repeat markers. The genetic constitution of the present samples was compared to that of faba bean samples collected by teams of the International Center for Agricultural Research in the Dry Areas (ICARDA) in the 1970s in the same region, and stored at the ICARDA gene bank. The results of the diversity analysis demonstrate that the recently collected samples and those stored at ICARDA largely overlap, thus demonstrating that over the past 50 years, little genetic change has occurred to the local faba bean populations examined. These findings suggest that farmers serendipitously applied international best practices for in situ conservation of agricultural crops.

IV.—Note on the Fossils from the Glacial Deposits of the North-West Coast of the Island of Lewis, Outer Hebrides

1876 ◽  
Vol 3 (12) ◽  
pp. 552-555 ◽  
Author(s):  
R. Etheridge
Keyword(s):  
West Coast ◽  
Long Island ◽  
The Other ◽  
Glacial Deposits ◽  
Geological Society ◽  
North West ◽  
The North ◽  
Outer Hebrides

In a paper, read before the Geological Society of London (June 25, 1873), “ On the Glacial Phenomena of the Long Island or Outer Hebrides,” Mr. James Geikie mentioned the occurrence of two descriptions of stony clay in the Long Island. The first of these deposits or “Bottom Till” occupies the low ground of the island, and is derived from the disintegration chiefly of gneissie rocks, and so far as observation went proved to be unfossiliferous. The other deposit was found in the north of Lewis, along the coast, and consists of two beds of unstratified stony clay containing fragments of shells, the lower resting on rock in situ.

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